Similar equipment already exists, e.g. that described in European patent No. 56 791 or U.S. Pat. No. 4,552,163, being the property of the applicant. With these devices, the instrument to be disinfected is placed vertically into a cylindrical chamber and jets of water and/or disinfectant mixed with air, are directed towards the vertical axis of the chamber and strike specific points of the front of the instrument. After striking the instrument, the jets rebound towards the walls of the chamber where gravity causes them to fall downwards. Consequently, there are a number of areas which are not sprayed or only partially sprayed by said liquids, thereby leaving an unwanted bacterial residue. This is particularly true in the lower part of the chamber where, in the case of dental instruments for example, there are usually areas which are more contaminated by germs. This is an unwanted and worrying problem.